1. Field of the Invention
The present invention relates to a numerical controller having a multiple-system numerical control section for controlling multiple systems of operation and a multiple-system sequential control section.
2. Description of Related Art
In the conventional numerical controller having a multiple-system numerical control section, sequence control is performed by a single-system sequential control section. When a peripheral device such as a workpiece loader or a pallet changer should be attached to a machine tool using the numerical controller of this type, a programmable logic controller (PLC) for sequence-controlling the peripheral device is added to control it.
There is known a numerical controller in which a CNC circuit is provided in a CNC board and a sequence control circuit is provided in the numerical controller itself so that a machine tool or the like is numerically-controlled by the CNC circuit and sequence-controlled by the sequence control circuit receiving miscellaneous function signals (M-function, T-function and the like) from the CNC circuit and/or a signal from a machine. In the numerical controller of this type, when a peripheral device should be added to a system without adding another PLC, another programmable control board (PC board) is added to the numerical controller to sequence-control the peripheral device. In this case, the CNC circuit and the sequence control circuit are originally interfaced. By interfacing the sequence control circuit provided in the numerical controller and the added PC board, all necessary parts of the system including the CNC circuit are interfaced each other (see JP 10-3307A).
Upgrading a system by adding a new peripheral device or the like to a numerical controller is increasing to meet a demand for automation at a plant or the like. However, in the conventional method, each time a new peripheral device is added to an existing numerical control system to upgrade it, a programmable logic controller (PLC) or a PC board needs to be added. This makes the structure of the system complicated and increases cost.